The yeast cytosolic thioredoxins are involved in the regulation of methionine sulfoxide reductase A.

Previously we have shown that the binding complex formation of methionine sulfoxide reductase A (msrA) promoter and calcium phospholipid binding protein (CPBP) enhances msrA transcription and expression. The msrA promoter-CPBP-binding complex (PmsrA-CPBP) formation was similar in Deltatrx1, Deltatrx2, and Deltatrx3 yeast strains and their control, with or without exposure to H(2)O(2). In Deltatrx1/Deltatrx2 double mutant the PmsrA-CPBP was similar to its parent strain, following exposure to H(2)O(2) for 30 min. However, a late-onset loss of PmsrA-CPBP binding activity occurred following exposure to H(2)O(2) for 24 hours. Hence, it was inferred that both Trx1 and Trx2 are involved in the PmsrA-CPBP formation during prolonged oxidative stress conditions. In addition, the survival rate of the Deltatrx1Delta/trx2 double mutant was approximately 10% of its parent strain when exposed to H(2)O(2.) The MsrA activity was obliterated in Deltatrx1/Deltatrx2 and Deltatrx1 strains and remained intact in the Deltatrx2 and Deltatrx3 strains. The msrA mRNA level in Deltatrx1 was significantly reduced in comparison to that of its control, slightly reduced in Deltatrx2, and unchanged in Deltatrx3, respectively. It is suggested that under normal growth conditions Trx1 is essential for msrA transcription and activity. Moreover, following long-term oxidative stress conditions, Trx1 and Trx2 appear to promote PmsrA-CPBP-binding activity and cell survival.

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